1. Field of the Invention
This invention relates to methods and apparatus for cleaning sock-like filter elements of a gas filtering apparatus with the filter elements in place.
2. Description of the Prior Art
In filters for gases, generally tubular or socklike filter elements made of woven cloth or needle felts or other natural or synthetic fibers are often used as filter media. Over a prolonged period, these filter elements can become clogged with solid particles or volatile organic constituents resulting in a gradual reduction in the volume flow of gas filtered through the system due to decreased permeability of the filter elements. As a result, more energy is required to maintain the system's operational pressure.
In order to remedy this situation several solutions have been proposed, including the use of polytetrafluoroethylene fibers for producing filter elements having "anti-adhesive" characteristics. While polytetrafluoroethylene filter elements are somewhat effective, they are relatively expensive and demonstrate poor mechanical strength in comparison to other fibers such as woven cloth or needle felts.
Another solution is the use of pneumatic or mechanical cleaning devices to clean the filter elements. As described in pending U.S. application Ser. No. 571,253, (filed Jan. 16, 1984), pneumatic or mechanical cleaning can be carried out periodically with the filter in operation and can effectively remove many particulates from the filter elements. However, solid particles and even volatile organic constituents can still accumulate over a prolonged period despite such cleaning because particulates, which generally accumulate on the external surfaces of the elements, can work their way into the fibers, reduce the permeability of the filters, increase the energy consumption of the filtering apparatus and reduce the overall efficiency of the operation.
Hence, the filter elements must periodically be removed from the apparatus and thoroughly washed. These washing operations are usually labor-intensive and sacrifice production because of extended periods of "down time." In addition, removal of the filter elements can be dangerous to health, especially where fine particulates are introduced in the breathing air of the technicians servicing the apparatus.